Conventionally, an illumination device that can emit planar light is known, and is utilized as a backlight unit for illuminating a liquid crystal display panel in a liquid crystal display device. As this type of illumination device for a liquid crystal display device, there are a direct-lit illumination device, a side-lit illumination device and the like.
The direct-lit illumination device refers to an illumination device in which a light source is arranged directly below a liquid crystal display panel. On the other hand, the side-lit illumination device refers to an illumination device in which a light guide plate is arranged directly below a liquid crystal display panel and in which a light source is arranged to face a predetermined side end surface of the light guide plate (for example, see patent document 1). In this side-lit illumination device, light is emitted from the light source, and then the light is introduced into the light guide plate through the predetermined side end surface of the light guide plate. Then, the light introduced into the light guide plate becomes planar light, and the planar light illuminates the liquid crystal display panel.
FIG. 7 is a simplified view of an example of a conventional side-lit illumination device. With reference to FIG. 7, in the conventional side-lit illumination device, a plurality of light emitting diode elements (LEDs) 101 are used as a light source. The LEDs 101 serving as the light source are combined into a module by being mounted on the same flexible printed circuit wiring board (FPC) 102.
A light guide plate 103 that converts light from the LEDs 101 into planar light is formed with a transparent plate-shaped member having four side end surfaces and front and back surfaces perpendicular to the four side end surfaces. A predetermined side end surface of the four side end surfaces of the light guide plate 103 is a surface that the LEDs 101 are arranged to face and that functions as an light entrance surface through which the light from the LEDs 101 is introduced into the light guide plate 103. The front surface of the light guide plate 103 is a surface that faces a liquid crystal display panel (not shown) and that functions as a light emitting surface through which the light introduced into the light guide plate 103 is emitted as planar light toward the liquid crystal display panel. Part of the FPC 102 (where the LEDs 101 are not mounted) is bonded to the back surface of the light guide plate 103, and thus the LEDs 101 are fixed to the light guide plate 103.